2.1Bankers Deque

Bankers Deques are Amortized double ended deques also known as deque
developed using Bankers method. Provides amortized running time of
O(1) for the operations
head, tail, last, init,
enqueue-front and enqueue.
Uses lazy evaluation and memoization to achieve the amortized running time.

2.3Real-Time Deque

Real-Time Deques eliminate the amortization by using two
techniques Scheduling and a variant of Global Rebuilding
called Lazy Rebuilding. The data structure gives a worst
case running time of O(1) for the operations
head, tail, last, init,
enqueue-front and enqueue.